The invention relates to a method of determining the position of an aircraft by combining inertial data with range data between the aircraft and satellites, in which: a) the range is stored in a FIFO memory so as make delayed range data available at the output from the memory; b) the delayed range data is combined with inertial data to obtain an estimate of position data for the aircraft; and c) a watch is maintained for the appearance of a fault in the range data, and when such a fault is detected, at least some of the data stored in the FIFO memory is modifying so as to be neutralized.
Legal claims defining the scope of protection, as filed with the USPTO.
1. A method of positioning a moving body by combining inertial data ({right arrow over (u)}) with data ({right arrow over ({circumflex over (r)} m ) concerning the ranges between the moving body and satellites, the method being characterized by the following steps: storing the range data in a FIFO memory ( 10 ) so as to have delayed range data available at the output from the memory; combining the delayed range data with the inertial data to obtain an estimate ({right arrow over ({circumflex over (x)}) for position data of the moving body; watching for the appearance of a fault (DSi) in the range data, and when such a fault is detected, modifying at least some of the data stored in the FIFO memory to reduce or eliminate its weight in the combination operation; and storing estimated satellite range data ({right arrow over ({circumflex over (r)}) as a function of inertial data and as a function of satellite ephemerides in a second FIFO memory ( 13 ) to have delayed estimates available at the output from said memory, the capacities of the two FIFO memories being equivalent so that the greatest delay value for the delayed estimate is identical to the greatest delay value for the delayed range data.
2. The memory according to claim 1 , in which the combining operation includes subtracting delayed estimates of the range data as a function of the inertial data from the delayed range data, and weighting the result of the subtraction.
3. The method according to claim 2 , in which the weighting gain (K) is constant.
4. The method according to claim 2 , in which the weighting gain (K) is variable.
5. The method according to claim 4 , in which the weighting gain is calculated as a function of the a priori covariance (R) of the errors affecting the range data, and as a function of the geometry of the constellation.
6. The method according to claim 1 , in which the value of the greatest delay is of the order of 1 to 6 s.
7. The method according to claim 1 , in which the storing and combination operations are performed at regular time intervals, at a frequency of the order of at least 0.5 Hz or at least 1 Hz.
8. The method according to claim 6 , in which each FIFO memory serves to record a plurality,—or tens—of successive data vectors ({right arrow over ({circumflex over (r)} m , {right arrow over ({circumflex over (r)}), each range data vector ({right arrow over ({circumflex over (r)} m ) comprising for each reception channel, i.e. for each satellite, a pseudo-range measurement together with the variance of the error affecting said measurement.
9. The method according to claim 1 , in which in order to neutralize the data stored in the first FIFO memory, the confidence associated with said data is decreased, in particular by increasing the covariance of the errors associated with the data.
10. An aircraft positioning device ( 18 ) that is mounted or mountable on board an aircraft, the device comprising: an inertial unit ( 14 ) delivering inertial data ({right arrow over (u)}); a unit ( 11 ) for receiving satellite ranges and ephemerides and delivering range and/or position data ({right arrow over ({circumflex over (r)} m ) to the unit ( 11 ); and a hybridization unit ( 12 , 13 , 16 , 17 , VPF) connected to the inertial unit to receive the inertial data and connected to the satellite range receiver unit to receive the range data, the hybridization unit delivering estimated position data ({right arrow over ({circumflex over (x)}) as a function of the inertial data and of the range data; the device being further comprises: a FIFO memory ( 10 ) coupled with (inserted between) the range receiver unit ( 11 ) and the hybridization unit, to deliver the hybridization unit with delayed range data; and a neutralization unit ( 15 ) responsive to fault data (DSi) representative of faulty range data coming from a faulty satellite (si), and arranged, in the presence of said fault data, to modify at least some of the range data stored in the memory, wherein the hybridization unit comprises: an estimator unit delivering estimated range data calculated on the basis of inertial data and estimated position data; a second FIFO memory ( 13 ) arranged to store the estimated range data and to output delayed estimated range data; a subtraction unit ( 16 ) arranged to subtract the delayed estimated range data from the delayed range data delivered by the first FIFO memory; and a weighting unit ( 17 ) arranged to weight the data delivered by the subtraction unit.
11. The device according to claim 10 , in which the hybridization unit comprises a recursive filter ( 12 ).
12. The device according to claim 11 , in which the recursive filter is a Kalman filter.
13. The device according to claim 10 , in which the neutralization unit ( 15 ) is connected to the range receiver unit ( 11 ) to receiver the fault data therefrom.
14. A program comprising code usable by a computer of a moving body to determine the moving body by combining inertial data ({right arrow over (u)}) with range data ({right arrow over ({circumflex over (r)} m ) between the moving body and satellites, the program being characterized by the following steps: storing the range data in a FIFO memory ( 10 ) to have delayed range data available at the output from the memory; combing the delayed range data with the inertial data in order to obtain an estimate ({right arrow over ({circumflex over (x)}) of position data for the moving body; and watching for the appearance of a fault (DSi) in the range data, and when such a fault is detected, modifying at least some of the data stored in the FIFO memory to reduce of eliminate its weight in the combination operation; and in which estimated satellite range data ({right arrow over ({circumflex over (r)}) is recorded as a function of inertial data in a second FIFO memory ( 13 ) to make delayed estimates available at the output from said memory, the capacities of the two FIFO memories being equivalent so that the value of the greatest delay for the delayed estimate is identical to the value of the greatest delay for the delayed range data.
15. A program usable by a computer of a moving body to determine the position of the moving body, the program being characterized in that it implements a method in accordance with claim 1 .
16. The method according to claim 7 , in which each FIFO memory serves to record a plurality,—or tens—of successive data vectors ({right arrow over ({circumflex over (r)} m , {right arrow over ({circumflex over (r)}), each range data vector ({right arrow over ({circumflex over (r)} m ) comprising for each reception channel, i.e. for each satellite, a pseudo-range measurement together with the variance of the error affecting said measurement.
17. The device according to claim 10 , in which the hybridization unit comprises a recursive filter ( 12 ).
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
February 12, 2007
March 22, 2011
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